Often, the successful operation of a rotating device is dependent on the ability to obtain proper alignment of the device rotational axis or axes. For example, with single or multiple axis rotating mechanical devices such as spacecraft unit positioners or pointing mechanisms, it is often required to measure and verify the rotational axes and defined centers of rotation of the rotating device.
Conventional techniques for determining the average axis of rotation can be ineffective and inaccurate. Prior art techniques typically rely upon manual operation and repeated readings, and are extremely slow. For example, a human observer may be required to align a single-point measuring device such as a telescope or theodolite multiple times on a limited number of targets to obtain approximate axis data.
What is needed in the art is an apparatus and method for determining the average axis and defined center of rotation for a rotating device that is accurate, time and cost efficient.
The present invention achieves technical advantages as a system and method for computing the rotational axis or axes and center(s) of rotation for a rotational device having one or more axes of rotation. In one embodiment, disclosed is a system for determining an average axis of rotation and center of rotation of a rotatable device having a plurality of target points affixed thereon. The system comprises a data collector adapted to obtain data from the device target points for a plurality of rotated positions, a transformer adapted to rotate and translate the obtained point data, and an iterative algorithm to position a secondary coordinate system to be coincident with the axis of rotation and center of rotation for one or more rotation axes of the rotatable device. The transformer and iterative algorithm can be applied sequentially to obtain each rotation axis and center of rotation of a multiple axis device using data from the data collector.
Also disclosed is an apparatus for determining an average axis of rotation and defined center of rotation for a rotatable device having a plurality of target points affixed thereon. The apparatus comprises a data collector adapted to obtain global coordinates of the target points at a plurality of rotations of the rotatable device, a transformer adapted to translate and rotate the obtained target point global coordinates, and an iterative algorithm to position a secondary coordinate system to be coincident with the rotatable device axis of rotation.
Further disclosed is a method for determining an average axis of rotation of a rotational device having a plurality of target points affixed thereon. The method comprises the steps of obtaining target point data from the plurality of target points and translating and rotating the obtained target point data to position a secondary coordinate system to be coincident with the axis and defined center of rotation of the rotatable device.
The present invention provides several advantages in measuring the rotational axis and locating the defined center of rotation of a rotatable body. The rotation axis location and defined center of rotation are calculatable with the use of the present invention. Rotational axis lateral runout and angular wobble errors may also be determined. Independent measurement of body rotations between point measurements is not required. The method may be applied to rotation ranges of less than one full revolution, if required by mechanism or facility limitations. The target point data location information is used directly, reducing complexity, inaccuracy and solution time compared with prior art methods that may lose information due to converting data to auxiliary vectors. The invention uses specific coordinate translations and Euler rotations to facilitate the generation of unambiguous location and orientation knowledge for a rotation axis having any arbitrary orientation in global coordinates. The accuracy of the present invention improves as the number of target points increases and as the radius from each target point away from the rotation axis increases.